Mexican Telescope Discovers Earth-Sized Exoplanet

With the Swiss-Mexican SAINT-EX telescope at the National Astronomical Observatory of San Pedro Mártir (Baja California) of the UNAM, scientists from this university participated in the discovery of the second exoplanet the size of the Earth, which revolves around an ultra-cool dwarf star.

Yilen Gómez Maqueo Chew, Laurence Sabin and Ilse Plauchu-Frayn, from the Institute of Astronomy, collaborated in the discovery of SPECULOOS-3b, with observations made in 2021 with SAINT-EX and followed up the work using the SPECULOOS network in 2022 and 2023.

Gómez Maqueo Chew pointed out that this is the second planetary system that has been found around an ultracool dwarf star. The first was TRAPPIST-1, discovered in 2016. But both are different.

The researcher abounded that the location of an exoplanet so different from the one previously seen in TRAPPIST-1 is important, as it reveals the differences in the types of planets around ultracold dwarf stars, so it is necessary to continue searching for them to achieve an understanding of the differences in sizes and forms of evolution of these systems.

The discovery, presented in the journal Nature Astronomy, stands out because although the ultracool dwarf stars are located in the solar neighborhood, SPECULOOS-3 has only one exoplanet, while TRAPPIST-1 has seven, all close together and similar in size.

The newly found planet has a radius close to that of the Earth (0.977) and, similarly to the Moon, its rotation is fixed by tides; both the period it takes to go around its star (year) and to go around its axis (day) is 17 hours, said Gómez Maqueo Chew.

The object was detected through the transit method, that is, the luminosity of the star is measured and the decrease or decrease in light detected in it -if periodic and consistent—indicates the presence of an object orbiting it.

The first observations made were with SAINT-EX in 2021, in which two transits were detected, which were particularly difficult to identify, as they are at the lower limit of what can be measured.

Subsequently, in 2022, data were obtained from the Artemis telescope in the Canary Islands — of the six that form the SPECULOOS network — and it was not until 2023, with a large amount of data gathered, that experts detected the presence of the transits.

Because the exoplanet was found using the transit technique, the mass of the object is unknown, an essential piece of information to know if it is as dense as Mercury or is like the Earth, said Gómez Maqueo Chew.

Stars like the one detected, despite being dwarfs and ultra-cold, have too much magnetic activity generating spots, and it is believed that they have more coronary mass ejections than those presented or registered by our Sun, which causes objects close to them to lose their atmosphere, as they constantly receive a lot of radiation and particles.

All this causes the planets to lose their atmosphere, especially the less massive ones that do not have as much capacity to retain their atmosphere by gravity. On the other hand, those that are very massive and close sometimes do, because they have more mass and the force of gravity is stronger. In this case, there is no possibility of it being a habitable world, argued Gómez Maqueo Chew.

The team of specialists, he added, has investigated the possibility that there are more similar or larger planets in this solar system with up to 10 days of orbital period, but because the newly located object generates a weak signal, it is difficult to find smaller ones, he added.

The SPECULOOS collaboration, of which SAINT-EX is part, and in which scientists and scientists from Mexico, Switzerland, Belgium and the United Kingdom participate, has located exoplanets orbiting red dwarf stars, but this is the first time they have discovered exoplanets in ultracool dwarfs, the main objective of the cooperation.